Men could do a lot to help their partners conceive simply by taking nutrition supplements.
Research on natural and complementary fertility treatments shows antioxidant supplements can improve men's sperm counts.
But there was no proof women's fertility could be boosted the same way.
The Cochrane Menstrual Disorders and Subfertility Group NZ reviewed more than 80 international studies on the effectiveness of alternative therapies.
Vitamins such as C and E, and minerals including zinc and magnesium can improve semen quality.
The amino acid glutathione or protein thioredoxin can also have a positive effect.
"These antioxidants are naturally occurring in semen," Auckland obstetrics and gynaecology professor Cindy Farquhar said.
"Subfertile men generally have lower levels so if you give them an antioxidant it will have an effect."
Low sperm levels account for 20 to 30 per cent of couples' fertility issues.
"For women it's more complex," Farquhar said.
"It's a little bit disappointing."
Studies on the effectiveness of acupuncture on live-birth rates through in vitro fertilisation (IVF) treatment also failed to show an improvement.
Chinese herbal medicine and other herbal remedy studies did not draw a strong conclusion either way, Farquhar said.
The studies encompassed more than 3000 couples, and up to 8000 individual women.
Subfertility, where conception is delayed by a year or more, affects one in six Kiwi couples.
Many couples opt for natural remedies when trying to conceive, or to complement medical interventions such as vitro fertilisation treatment (IVF).
But Farquhar said the findings confirmed women should be cautious on which supplements they take when trying to conceive.
"Women have a window of opportunity to get pregnant and should do everything to maximise that opportunity.
"Don't waste it on something that doesn't work."
The findings come amid a trans-Tasman study on the use of acupuncture during IVF.
Auckland clinic Fertility Plus is involved in the randomised controlled trial with the University of Western Sydney's Centre for Complementary Medicine Research.
More than 1000 women are being recruited for the study.
Farquhar will present the Cochrane Collaboration findings at the Charms and Harms of Natural Medicine free winter lecture series at Auckland University.
The Hype or Hope? public lecture runs tomorrow from 1pm to 2pm at the Maidment Theatre.
- © Fairfax NZ News
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